Center of gravity device



L. O. SPAULDING CENTER OF GRAVITY DEVICE Filed March 15, 1946 Dec. 27, 1949 ELWPEHEE vlj. Spaulding Patented Dec. 27, 1949 UNITED STAT ES PAT QL'FFICE..

CENTER 0F GRAVITY DEVICE' Lawrence 0. Spaulding, Longmeadow,.Massi Application March I5, 1946', Serial' No. 654,789

(Granted under the act of March 3', 1883,. as

amended prilStl, 1928; 370 0. G. 757') The inventionr described` herein` may be. manu-3 factured: and'. used by or for the Government for governmental purposes, withoutA the payment to me of any royalty thereon.y

This invention rela-testoa device for determining the. center of gravity oi anobject.

Accurate determination et the center of grav-l ity of irregularly shaped: objects has been accom plis-lied only with diiiiculty by known methods- Inthe rstfplace, suchy objects are somewhat diiilcult tov support while. attempting. to determine the center of gravity thereof and, secondly, even. when such objeetsare properlysupported, deter-vmination. of the center of gravity thereof is not. alwaysprecise.. One procedure for graphically determining. the center of gravity of an irreguf. larly shaped object` isv to suspend such object in a number of differenty positions. and from. each. point of suspension. drop a plumb line.. The intersection of such plumb lines is intended to determine theI center of gravity of the object. It. sobviousr however. that.- such determination is. cumbersomey and somewhat inaccurate..

Accordingly, it is an object ofY this invention to provide a device for accurately determining the center off gravity of' any object. adapted for mounting onsuch device.

A particular object of this invention is-y to pro. vide. a device for determining the centerv of grav ity of a U.. S. Browning type machine gun.

The specific nature ofthe invention as well as other objects and advantages thereof will clearly appear from a description oa preferred'embodi-- ment as shown in the accompanying drawing in which:

Fig. I is a front view of the assembly;

Fig. 2` is a partial side view of the assembly of' the center ofv gravity machine;

Fig. 3 is a diagrammatic sketch ofi the rightside up mounting of a. gun, andthe angle derived" thereby;

Fig. 4 is a diagrammatic sketch of'the upside. down` mounting of a. gun, and the angle derived thereby; and

Fig. 5 isanv enlarged. view at D in Fig. 4`.

In Fig. 1 there is shown in assembled= relation. a center of gravity device embodying this invention. Such device comprises essentially a largev diameter wheel I mounted on a horizontal shaftv 2A by means of a nut 9 and washer 8' the nut 9` ,y

being threadably secured to the end portion IIJ'" of the shaft 2. A housing. 3' provided with. 'xed'; bearings (not shown)` supports shaftV 2- in such manner that free. rotation of' the shaft is thereby obtained. The entire assembly is arranged to` be secured to a. table or other means lof4 support.- by bolts which areinsertedl through suitable holes 4 provided in outwardly extending anges 5 depending from the` lower edges of. housing 3.

According to the preferred form of this inven- .mounting pin I8 engaging hole 2'I.

tion, the. wheelv I is provided with a centrally dis-- posed'v hub.7 t asshown in Fig. 2 from which exe tenda plurality oi radially disposed'` spokes l con-f nesting. such` hub withI a rim 25.. The face: ofv such rim near the*y outer periphery thereof isgraduated inV degrees as shown at II.. A bracket. lf3, secured to the housing 3 by screws I-ll as shown in` Fig. 2,` is-provided to. mounta horizontally disposed index pointer i2 on the verticalv axis of wheel I. Screws I5v securey such pointer toi bracket I3.

It. is desired to point` out that thel wheel- I can be fabricated as a singie disk. Qbviousl-y,` what-f ever construction is desired.. the wheel mus-t be` balanced to a high.. degree of. sensitivity in orderi to obtain the advantages of this invention.

Three horizontally disposed mounting'pins I, IT, and lfd extending substantialiy at'right ang-les' from wheel I are secured thereonL by nuts 22', 23

- and 24 screwed onto the rear end threaded por'- tions I9, 20, and 2I of the mounting pins IG; IT, and I8. Pin I'I is mounted on the spoke l* which is disposed opp'osit'ethe zero position of the graduations II inscribed on rim 25. Pins. t6 and I8 w are mounted on rim 25 to the right andv leftrey following description ofthe method of determining the center of gravity of an objectr such gun. is utilized as an' example. However., this is.

only a specific illustration and should not be con' strued as limiting this invention solely to such.

use. f For such rearm it has been found that two readings yield sufficient data for' the solving of certain mathematical formulas, as will later be shown herein. The methods ol" mounting the Browning type machine gun 26' are' shown in Figs. 3 and 4. The holes 21 and. 28 used' for engaging the mounting pins I6, I1, and I8 are thosek normally utilized toY mount the gun 26 on a tri'- pod or other support. In the' event it is desired' to use that portion of scale II which appears on the bottom half of wheel I, there are provided'.

alternate pins 30, 3| and 32 which maybe used to determine the. center of gravity of' an object in a manner similar to that about to be explained.

for pins I6, I1 and I'8.

The rst reading necessary to determine the center of gravity of gun26 is obtained by mounting said gun right-*side up on. wheel I as shown in Fig. 3, mounting pin l1 engaging hole. 28- and Wheel I is then permitted to rotate dueto the weight of gun 26 until the wheel I comes. to a state of rest with the gun- 26 assuming. substantially the position as. shown: in- Fig.. 3. InY suchI position-,. the angle A shownV` therein can bereadg directly from.

the graduated scale II of wheel I. Such angle is conveniently determined inasmuch as pin I1 is located on'the spoke 'l which has the 0 graduation mark at the top thereof and when the wheel I is in its non-working position, the mark is directly under the pointer I2. Thus when the gun 2B mounted on wheel I comes to rest, angle A can be read directly opposite the pointer I2 and is the amount of rotation from the vertical axis in degrees. If a perpendicular is dropped to the longitudinal axis of the gun from the 0 mark to trunnion hole 28, angle A can be laid off from the 0 mark and the side thereof inscribed on the gun.

For the second reading the gun is removed from the mounting pins and then mounted upside down on wheel I as shown in Fig. 4. Pin I6 engages hole 21 while pin I1 re-engages hole 2B. The wheel is then permitted to rotate until it cornes to a state of rest and the angle B may be read directly on the graduated scale I I in a manner similar to that described for the first reading. If angle B is laid off in the same manner as that described for angle A, the intersection on the gun of the sides of the angles will indicate the center of gravity.

On the other hand, by substituting the values of the angles thus found in the formulas shown below, measurements locating the center of gravity of gun 26 are readily determined.

a is constant Angle A and B as determined from device (A is always larger) b=a tan A ar=a tan A-a tan B 31:2. cos(90-B) b+y=horizontal distance from adapter hole v=vertical distance from adapter hole When the values of b'-ly and v have been determined such distances can 'be readily laid out on gun 26 from hole 28 and thereby locate the desired center of gravity as shown at CG in Fig. 4.

Thus it is readily apparent that there is here provided a device whereby the center of gravity of any object capable of being mounted hereon can be conveniently and accurately determined.

I claim:

l. A device for determining the center of gravity of any object arranged for mounting thereon and having mounting holes therefor, comprising a lbalanced wheel arranged to rotate freely, there being a series of graduation marks including a zero mark inscribed on the rim of said wheel, indexing means iixedly secured to a non-rotating portion of the device and arranged to indicate the amount of angular displacement thereof from a zero position, and a plurality of mounting pins removably secured to said wheel and arranged to maintain the balance of said wheel, one of said pins being secured to said wheel a fixed radial distance from said zero mark, the remaining pins secured to said wheel on both sides of said radially xed pin at distances therefrom corresponding to the linear distance between the particular mounting hole in the object selected to receive said radially fixed pin and each of said remaining holes whereby at least 4 two successive and different mountings of the object on said mounting pins effect corresponding angular displacements of said wheel from which trigonometric relations can be set up for evaluation of distances which when measured from the aforementioned particular mounting hole serve to determine the center of gravity of the object. 2. A device for determining the center 0f gravity of any object arranged for mounting thereon and having mounting holes therefor, comprising a balanced wheel rotatably mounted on a horizontal shaft, said wheel having a hub and a plurality of spokes radiating therefrom, there being a series Iof graduation marks inscribed on the rim of said wheel, said graduation marks including a centrally located zero mark, an index pointer iixedly secured to a non-rotating portion of the device and arranged to align with said zero mark when said wheel is in a non-operative position, and a plurality of mounting pins removably secured to said wheel and arranged to maintain the balance of said wheel, one of said pins being secured to one of said spokes in radial alignment with said zero mark and at a fixed distance therefrom, the remaining pins being secured to said wheel on both sides of said radially fixed pin at distances therefrom corresponding to the linear distances between the particular mounting hole in the object selected to receive said radially fixed pin and each of said remaining holes whereby at least two successive andy different mountings of the object effect corresponding angular displacements of said wheel from which trigonometric relations can be set up for evaluation of distances which when Ineasured from the aforementioned particular mounting hole along the longitudinal and vertical axes of the object serve to determine the center of gravity of the object. Y

3. A device for determining the center of gravity of a gun having a front and rear mounting hole, comprising a housing, a horizontally disposed shaft rotatably secured in said housing and having one end extending therefrom, a balanced wheel xedly mounted to said free end of said horizontal shaft, said wheel having a hub and a plurality of spokes radiating therefrom, there being a series of graduation marks inscribed on the rim of said wheel, said graduation marks including a centrally located zero mark, an index pointer fixedly secured to said housing and arranged to align with said zero mark when said wheel is in a non-operative position, and a plurality of mounting pins removably secured to said wheel and arranged to maintain the balance of said wheel, one of said pins being secured to one of said spokes in radial alignment with said zero mark and at a xed distance therefrom, the remaining pins ybeing secured to said wheel on both sides of said radially xed pin at distances therefrom corresponding to the linear distance between the gun mounting holes whereby mounting the gun on said pins in at least two reversed positions eiects corresponding angular displacements of said zero mark from said index pointer, the values of said angular displacements arranged for substitution in trigonometric formulas to indicate distances which when measured along the horizontal and vertical axes of the front mounting hole establish a point determining the center of gravity of the gun.

LAWRENCE O. SPAULDING.

No references cited. 

